Device for adjusting the pumping capacity of a lubricant pump for an internal combustion engine

ABSTRACT

A system for controlling the pumping capacity of a lubricant pump for an internal-combustion engine, having a vane cell pump ( 2 ) which has a rotor body ( 4 ), rotor blades ( 10 ) which can be radially displaced in the rotor body as well as a lifting ring ( 12 ) (stator) whose position can be adjusted with respect to the axis of rotation of the rotor for changing the delivery volume as a function of operating parameters of the internal-combustion engine. The lifting ring ( 12 ) is linked to an adjusting piston ( 28 ) guided in a valve bore ( 30 ) of a pressure regulating valve ( 26 ), which adjusting piston ( 28 ) is acted upon by engine oil pressure on a piston front side ( 34 ), the piston front side ( 34 ) being connected with the piston rear side ( 37 ) by way of a throttle bore ( 62 ).

This Application claims priority to International Patent Application No.PCT/EP03/06971, filed Jul. 1, 2003, designating the United States ofAmerica, and German Application DE 102 39364.8 filed on Aug. 28, 2002,the entire disclosure of which is incorporated herein by reference.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a system for controlling the pumping capacityof a lubricant pump for an internal-combustion engine.

It is generally known, in the case of internal-combustion engines, touse rigidly driven oil pumps for supplying the oil circulating system,which oil pumps are constructed, for example, as external gear pumps orinternal gear pumps or as vane cell pumps. These are oil pumps with avariable or constant delivery volume per pump wheel rotation. So-calledconstant-delivery pumps are equipped with a pressure limiting valve, bymeans of which the maximal oil pressure can be adjusted. When the oilpressure limiting valve opens at a maximal oil pressure which is setbeforehand, the excess oil volume is returned into the low-pressure partof the oil pump.

Since the oil volume flow required for the lubrication of the engine isnot always proportional to the rotational speed of the engine or to therotational speed of the pump, suggestions have been made that the oilpressure be controlled in order to be able to reduce the driving powerof the engine oil pump particularly in the partial load range. Thus, forexample, from Japanese Patent Document JP-OS 9-885 33, a system is knownfor controlling the oil pressure of a gear pump in the case of which abypass of the gear pump monitored by the pressure regulating valve canbe opened or closed as a function of the pressure. For this purpose, thepiston head is provided with an opening or throttle which is connectedwith an interior constructed on the rear side of the piston valve. Acontrol valve is connected in front of the interior of the piston valve,by means of which control valve, the differential pressure existingbetween the forward and rear side of the piston valve can be changed andtherefore the opening oil pressure can be adjusted.

From German Patent Document DE 43 02 610 A1, a vane cell pump is knownwhich has a variable delivery volume and in the case of which the volumeflow can be adjusted by a change of the position of the lifting ringwith respect to the axis of rotation of the rotor. Furthermore, inaddition to the pure maximal oil pressure limitation or of the deliveryvolume control, an additional limitation of the delivery volume as afunction of the temperature and/or the rotational speed of the engine issuggested. For this purpose, high-expenditure temperature-dependentcontrol elements as well as additional pressure control systems arerequired which, in addition to the maximal oil pressure limitation,cause an adjustment of the lifting ring of the vane cell pump andtherefore, as required, a reduction of the delivered oil volume flow.

It is therefore an object of the invention to provide a system for avolume-flow-controlled vane cell pump by means of which a lubricatingoil supply of the internal-combustion engine which meets therequirements takes place in a simple manner, so that the taken-up powerof the oil pump can be reduced as a result of a lowering of the oilpressure in certain operating conditions.

By means of the suggested system, the driving power required for thelubricating oil supply of the internal-combustion engine in the case ofa vane cell pump can be controlled in a simple manner as a function ofoperating parameters of the internal-combustion engine. As a result, theoil pressures required for the various operating conditions of theengine can be adjusted or adapted, so that another fuel saving potentialexists because of the reduced taken-in power in comparison to anuncontrolled oil pump. The suggested system for reducing the oilpressure can be retrofitted in a simple manner in the case of vane cellpumps which are already in operation.

The force directed against the engine oil pressure on the piston rearside of the pressure regulating valve is generated by a flat coil springwhich is guided and supported in a receiving opening provided on therear side of the piston.

For the pressure-dependent controlling of the oil volume flow, a valveelement is integrated in a hydraulic pipe leading from the regulatingvalve to the tank, by way of which regulating valve the oil flow can beadjusted which can be returned to the suction side of the oil pump.

The oil pressure or the oil volume flow delivered by the oil pump iscontrolled as a function of operating parameters of theinternal-combustion engine, such as the rotational speed, the load orthe engine oil temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention is illustrated in the drawings.

FIG. 1 is an overall schematic view of a system for controlling thepumping capacity of a vane cell pump in a first operating position;

FIG. 2 is a view of the system in a second operating position;

FIG. 3 is a graphic representation of an operating-point-dependent oilpressure control; and

FIG. 4 is a block diagram for a calibrated oil pressure control.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The vane cell pump 2 schematically illustrated in FIGS. 1 and 2 has arotor 4 which is non-rotatably connected with a drive shaft 6. In therotor 4, recesses 8 are provided which extend radially to the outsideand in which longitudinally displaceable rotor blades 10 are received ina known manner. The rotor 4 and the rotor blades 10 received therein aresurrounded by a lifting ring 12, so that corresponding oil deliveryspaces 14 are constructed between the rotor 4, the lifting ring 12 andbetween two respectively adjacent rotor blades 10. The lifting ring 12is swivellably about an axis 16 disposed on a housing-fixed point. As aresult, its position is unchanged with respect to the axis of rotationof the rotor for adjusting a defined oil delivery quantity per rotation.For this purpose, the lifting ring 12 has a linked tongue 18 which issituated opposite the bearing axis 16 and which is equipped with aguiding pin 20 interacting in the manner of a connecting link guide witha link window 22 of an adjusting rod 24. The adjusting rod 24 is linkedto the outer circumference of an adjusting piston 28 guided in apressure regulating valve 26.

Between the housing 32 and the piston front side 34, a first pressurechamber 36 is formed which is connected with the delivery side of thevane cell pump 2. On the piston rear side 37, a receiving opening 38 isprovided in the adjusting piston 28, in which receiving opening 38, aflat coil spring 40 is accommodated or guided. On one its ends, the flatcoil spring 40 is supported at the bottom of the of the piston rear side37 and, on its other end, the flat coil spring 40 is supported at aclosing element 42 of the pressure regulating valve 26. Between theclosing element 42 and the piston rear side, a second pressure chamber44 is constructed which is connected with the input 50 of a regulatingvalve 52 by way of an opening 42 provided in the closing element 46 anda hydraulic pipe 48 connected thereto. The input 50 of the regulatingvalve 52 is monitored by an adjusting piston 54 which is controlled by asolenoid 56 provided at the regulating valve 52. The output 58 of theregulating valve 52 is connected with the oil tank or the oil reservoir60 of the internal-combustion engine into which the suction side of thevane cell pump 2 leads, in turn. The two pressure chambers 36 and 44constructed in the pressure regulating valve 26 are connected by way ofa throttle which is constructed in the adjusting piston 28 and which, inthe present embodiment, is a stepped bore 62.

In the following, the method of operation of the system for controllingthe pumping capacity of the vane cell pump will be explained in detail.As a function of operating parameters, which will be explained in detailby means of the control diagram in FIG. 3, the vane cell pump, which isrigidly driven by the engine of the internal-combustion engine, deliversa defined oil volume flow to the consuming devices of theinternal-combustion engine. In this case, the pressure chamber 36 of thepressure regulating valve 26 is connected with the delivery side of thevane cell pump 2. As a function of the oil pressure existing in thefirst pressure chamber 36, the position of the lifting ring 12 relativeto the axis of rotation of the rotor and thus the oil delivery quantityper rotation of the rotor are adjusted. As a result, as generally known,the oil volume flow delivered by the vane cell pump 2 is adjustedcontinuously between a maximal delivery quantity (see FIG. 1) and a zerodelivery quantity (see FIG. 2). As explained initially, by means of thecontrolling of the pressure regulating valve 26 explained in detail inthe following, for a further reduction of the taken-up driving power ofthe vane cell pump 2, as a function of operating parameters, such as therotational speed, the oil temperature or the load condition of theinternal-combustion engine, the oil delivery quantity and thus the oilpressure can be adapted for reducing the taken-up driving power. Theadjusting piston 54 of the regulating valve 52 is controlled by way of acharacteristic curve diagram stored in the engine control unit. In theposition of the adjusting piston 54 illustrated in FIG. 1, the input 50of the regulating valve 52 is completely closed. As a result, thepressure in the first and in the second pressure chamber 36, 44 is thesame, so that, because of the flat coil spring 40, the adjusting piston28 takes up a position within the valve bore 30, in which theeccentricity of the position of the lifting ring 12 relative to the axisof rotation of the vane cell pump 2 is maximal. When the adjustingpiston 54 opens up the input 50 (see FIG. 2), a certain oil volume flowflows via the stepped bore 62 by way of the hydraulic pipe 48 to the oilreservoir 60 and thus flows off to the suction side of the vane cellpump 2. As a result of the throttling effect of the stepped bore 62, adifferential pressure is generated between the piston front and rearside 34, 37, so that the pressure in the second pressure chamber 44 islowered with respect to that in the first pressure chamber 36. Thus, theadjusting characteristic of the adjusting piston 28 changes and thelatter, as illustrated in FIG. 2, is moved against the force of the flatcoil spring 40 in the direction of the closing element 42. As a result,by way of the adjusting rod 24 and the linked tongue 18, the position ofthe lifting ring 12 relative to the axis of rotation of the rotor ischanged such that the oil delivery quantity of the vane cell pump 2 andthus the oil pressure is reduced. Corresponding to the characteristiccurve diagram which is illustrated in FIG. 3 and filed in the enginecontrol unit, as a function of the oil temperature and the rotationalspeed of the internal-combustion engine, arbitrary oil volume flows canbe adjusted which are adapted to the corresponding oil pressure demandof the engine. Thus, for example, at low rotational speeds, a clearlylower oil pressure is required for a sufficient bearing supply than athigh rotational speeds. Extremely high or low oil temperatures require ahigher oil pressure in order to, on the one hand, meet the highercooling requirement of the bearings and, on the other hand, be able tocompensate the pipe pressure loss and the bearing intake pressure at lowoil temperatures. Furthermore, in the case of a high load condition ofthe engine signalled by the position of the throttle valve, a higher oilpressure is required than at lower and medium loads.

In the case of engines using cooling jet nozzles for the piston cooling,which nozzles open at a certain threshold oil pressure, it now becomespossible to control the piston jet nozzles by way of the characteristicdiagram filed in the engine control unit. Additionally, the frictionlosses are reduced thereby and the delivery flow required for supplyingthe engine is reduced.

In connection with the suggested operating-point-dependent oil pressurecontrol, a self-calibration is also provided. As illustrated by means ofFIG. 4, the desired oil pressure is compared in this case with theactual oil pressure. If the actual oil pressure deviates from thedesired oil pressure by a previously defined Δp, the control curve isshifted by a correction factor until the Δp corresponds to the definedcriterion. Background for the provided self-calibration is the fact thatthe oil demand of the engine changes during its service life as a resultof a bearing wear, a pump wear or a changing oil viscosity.

1. A system for controlling the pumping capacity of a lubricant pump foran internal-combustion engine, comprising: a vane cell pump including arotor body with rotor blades radially displaced in the rotor body and alifting ring whose position is adjustable with respect to the axis ofrotation of the rotor to change an oil delivery volume as a function ofoperating parameters of the internal-combustion engine, an adjustingpiston operatively linked to said lifting ring, and guided in a valvebore of a pressure regulating valve, wherein said adjusting piston isacted upon by engine oil pressure on a piston front side with the pistonfront side being connected with the piston rear side by way of athrottle bore in the adjusting piston; a pressure chamber on theadjusting piston rear side in which a spring element is located; and ahydraulic pipe connected to the pressure chamber and via a regulatingvalve to a suction side of the lubricant pump such that a deliveryvolume of the vane cell pump is variable as a function of an oil volumeflow though the throttle bore, wherein, for an operating-point-dependentoil pressure control of the vane cell pump, a characteristic curvediagram is stored in a control unit, by means of which characteristiccurve diagram, the oil pressure is defined as a function of therotational speed, the engine oil temperature or the load condition ofthe internal-combustion engine.
 2. The system according to claim 1,wherein the adjusting piston rear side has a receiving opening in whichthe spring element is at least partially guided and supported.
 3. Thesystem according to claim 1, wherein the regulating valve arranged inthe hydraulic pipe provides for adjustment of oil flow to be returned toa suction side of the vane cell pump.
 4. The system according to claim3, wherein the operating parameters of the internal-combustion engineinclude at least one of rotational speed, load and engine oiltemperature.
 5. The system according to claim 1, wherein thecharacteristic curve diagram is calibrated by a correction factor.
 6. Asystem for controlling the pumping capacity of a lubricant pump for aninternal-combustion engine, comprising: a vane cell pump including arotor body with rotor blades radially displaced in the rotor body and alifting ring whose position is adjustable with respect to the axis ofrotation of the rotor to change an oil delivery volume as a function ofoperating parameters of the internal-combustion engine, an adjustingpiston operatively linked to said lifting ring, and guided in a valvebore of a pressure regulating valve, wherein said adjusting piston isacted upon by engine oil pressure on a piston front side with the pistonfront side being connected with the piston rear side by way of athrottle bore in the adjusting piston; a pressure chamber on theadjusting piston rear side in which a spring element is located; and ahydraulic pipe connected to the pressure chamber and via a regulatingvalve to a suction side of the lubricant pump such that a deliveryvolume of the vane cell pump is variable as a function of an oil volumeflow though the throttle bore, wherein the adjusting piston rear sidehas a receiving opening in which the spring element is at leastpartially guided and supported, wherein, for anoperating-point-dependent oil pressure control of the vane cell pump, acharacteristic curve diagram is stored in a control unit, by means ofwhich characteristic curve diagram, the oil pressure is defined as afunction of the rotational speed, the engine oil temperature or the loadcondition of the internal-combustion engine.
 7. A system for controllingthe pumping capacity of a lubricant pump for an internal-combustionengine, comprising: a vane cell pump including a rotor body with rotorblades radially displaced in the rotor body and a lifting ring whoseposition is adjustable with respect to the axis of rotation of the rotorto change an oil delivery volume as a function of operating parametersof the internal-combustion engine, an adjusting piston operativelylinked to said lifting ring, and guided in a valve bore of a pressureregulating valve, wherein said adjusting piston is acted upon by engineoil pressure on a piston front side with the piston front side beingconnected with the piston rear side by way of a throttle bore in theadjusting piston; a pressure chamber on the adjusting piston rear sidein which a spring element is located; and a hydraulic pine connected tothe pressure chamber and via a regulating valve to a suction side of thelubricant pump such that a delivery volume of the vane cell pump isvariable as a function of an oil volume flow though the throttle bore,wherein the regulating valve arranged in the hydraulic pipe provides foradjustment of oil flow to be returned to a suction side of the vane cellpump, wherein, for an operating-point-dependent oil pressure control ofthe vane cell pump, a characteristic curve diagram is stored in acontrol unit, by means of which characteristic curve diagram, the oilpressure is defined as a function of the rotational speed, the engineoil temperature or the load condition of the internal-combustion engine.8. A system for controlling the pumping capacity of a lubricant pump foran internal-combustion engine, comprising: a vane cell pump including arotor body with rotor blades radially displaced in the rotor body and alifting ring whose position is adjustable with respect to the axis ofrotation of the rotor to chance an oil delivery volume as a function ofoperating parameters of the internal-combustion engine, an adjustingpiston operatively linked to said lifting ring, and guided in a valvebore of a pressure regulating valve, wherein said adjusting piston isacted upon by engine oil pressure on a piston front side with the pistonfront side being connected with the piston rear side by way of athrottle bore in the adjusting piston; a pressure chamber on theadjusting piston rear side in which a spring element is located; and ahydraulic pipe connected to the pressure chamber and via a regulatingvalve to a suction side of the lubricant pump such that a deliveryvolume of the vane cell pump is variable as a function of an oil volumeflow though the throttle bore, wherein the operating parameters of theinternal-combustion engine include at least one of rotational speed,load and engine oil temperature, wherein, for anoperating-point-dependent oil pressure control of the vane cell pump, acharacteristic curve diagram is stored in a control unit, by means ofwhich characteristic curve diagram, the oil pressure is defined as afunction of the rotational speed, the engine oil temperature or the loadcondition of the internal-combustion engine.